[PATCHv2 2/2] pSeries/papr_scm: buffer pmem's bound addr in dt for kexec kernel

[Pingfan Liu <kernelfans@gmail.com>]

At present, plpar_hcall(H_SCM_BIND_MEM, ...) takes a very long time, so
if dumping to fsdax, it will take a very long time.

Take a closer look, during the papr_scm initialization, the only
configuration is through drc_pmem_bind()-> plpar_hcall(H_SCM_BIND_MEM,
...), which helps to set up the bound address.

On pseries, for kexec -l/-p kernel, there is no reset of hardware, and this
step can be stepped around to save times.  So the pmem bound address can be
passed to the 2nd kernel through a dynamic added property "bound-addr" in
dt node 'ibm,pmemory'.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Oliver O'Halloran <oohall@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andrew Donnellan <ajd@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: kexec@lists.infradead.org
---
note: This patch has not been tested since I can not get such a pseries with pmem.
      Please kindly to give some suggestion, thanks.

 arch/powerpc/platforms/pseries/papr_scm.c | 32 +++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 0b4467e..40cd214 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -14,6 +14,7 @@
 #include <linux/delay.h>
 
 #include <asm/plpar_wrappers.h>
+#include "of_helpers.h"
 
 #define BIND_ANY_ADDR (~0ul)
 
@@ -383,7 +384,7 @@ static int papr_scm_probe(struct platform_device *pdev)
 {
 	struct device_node *dn = pdev->dev.of_node;
 	u32 drc_index, metadata_size;
-	u64 blocks, block_size;
+	u64 blocks, block_size, bound_addr = 0;
 	struct papr_scm_priv *p;
 	const char *uuid_str;
 	u64 uuid[2];
@@ -440,17 +441,28 @@ static int papr_scm_probe(struct platform_device *pdev)
 	p->metadata_size = metadata_size;
 	p->pdev = pdev;
 
-	/* request the hypervisor to bind this region to somewhere in memory */
-	rc = drc_pmem_bind(p);
+	of_property_read_u64(dn, "bound-addr", &bound_addr);
+	if (bound_addr) {
+		p->bound_addr = bound_addr;
+	} else {
+		struct property *property;
+		u64 big;
 
-	/* If phyp says drc memory still bound then force unbound and retry */
-	if (rc == H_OVERLAP)
-		rc = drc_pmem_query_n_bind(p);
+		/* request the hypervisor to bind this region to somewhere in memory */
+		rc = drc_pmem_bind(p);
 
-	if (rc != H_SUCCESS) {
-		dev_err(&p->pdev->dev, "bind err: %d\n", rc);
-		rc = -ENXIO;
-		goto err;
+		/* If phyp says drc memory still bound then force unbound and retry */
+		if (rc == H_OVERLAP)
+			rc = drc_pmem_query_n_bind(p);
+
+		if (rc != H_SUCCESS) {
+			dev_err(&p->pdev->dev, "bind err: %d\n", rc);
+			rc = -ENXIO;
+			goto err;
+		}
+		big = cpu_to_be64(p->bound_addr);
+		property = new_property("bound-addr", sizeof(u64), &big, NULL);
+		of_add_property(dn, property);
 	}
 
 	/* setup the resource for the newly bound range */
-- 
2.7.5